This invention concerns a support for a recording material for the ink-jet printing process.
The ink-jet recording method is an electronic printing method which has already been described repeatedly. It is used in a broad field of applications for production of color graphics, color images and also for printing text. High demands are made of the recording materials used with this technology. These include, for example, a high ink density, high resolution, short ink drying times, light stability and dimensional stability. Surface gloss is another important demand for commercial applications. This is important especially in the production of art graphics. However, gloss is also an important requirement in production of images where a photographic quality is required.
EP 650 850 A discloses a recording material consisting of a polyolefin-coated base paper and a receiving layer. This recording material permits the production of images with a high resolution and ink density and a high gloss which are comparable in the overall impression to conventional photographic images. One disadvantage of the polyethylene-coated support is the poor uptake of ink fluid due to the fact that the paper is sealed with a plastic, which leads to poor drying behavior of the recording material. In addition, the limited recyclability of such a polyolefin-coated support material should not be forgotten.
EP 709 221 A proposes a recording material containing a paper substrate with a certain Sheffield water-soluble components, where the total recording material has a gloss of more than 50, measured at an angle of 60 xc2x0.
In a few other publications, glossy recording materials are claimed, where the receiving layer is pressed against a heated mirror-smooth cylinder surface in a cast-coating operation, so the recording material is given a high-gloss surface.
The object of this invention is to create a support for an ink-jet recording material suitable for any type of ink receiving layers on which especially glossy photographic quality images can be produced with conventional ink-jet inks. In addition, the object of this invention is to propose a recording material for ink-jet printing methods that can be produced with the help of the above-mentioned support.
These objects are achieved by a support for an ink-jet recording material containing a base paper having on at least one side a layer containing barium sulfate and microbeads.
Hollow polymer microbeads of a thermnoplastically deformable plastic based on polystyrene-acrylate and styrene or acrylic resin are especially suitable. The microbeads have a diameter of at least 0.2 xcexcm. Microbeads with a diameter of 0.4 xcexcm to 5 xcexcm are especially suitable.
The microbead content in the layer containing barium sulfate may be 1 to 70 wt %, based on the layer. Especially good results were obtained with a microbead content of 20 to 50 wt %.
The binder used in the above-mentioned layer may be selected from the group of hydrophilic colloidal and/or water-soluble binders such as polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide, gelatin, starch, starch derivatives, polyvinyl acetate, polyethylene glycol, cellulose esters, proteins, alginates, polyacrylic acid or mixtures of these binders.
The coating weight of the layer is 10 to 50 g/m2, in particular 15 to 25 g/m2. The base paper has a raw paper core which is produced preferably by using chemical pulp or pulp mixtures with a short fiber content of 80 to 98 wt %, in particular 85 to 95 wt % (unbeaten pulp).
Hardwood pulp mixtures with a fiber length of 0.50 to 0.60 mm (unbeaten pulp) or 0.40 to 0.50 mm (with a degree of beating between 25 and 35xc2x0 SR) are especially suitable. The pulp mixture according to this invention has in particular a degree of beating of 28 to 32xc2x0 SR (measured according to Schopper-Riegler).
The raw paper may also contain other substances such as a sizing agent and fillers. In principle, all conventional compounds for paper making can be used as sizing agents and wet strength agents. In a special embodiment of this invention, the raw paper contains kaolin and calcium carbonate in a ratio of 2:1 to 1:2 and has a Cobb value of 20 to 100. The raw paper may also be surface-sized with starch, gelatin or polyvinyl alcohol. The basis weight of the raw paper is 60 to 220 g/m2, in particular 80 to 160 g/m2.
It has been found that by using the pulp mixture which is specified in detail and by using the filler with a simultaneous reduction in the amount of sizing agent, it is possible to produce a base paper with which a recording material with very good dimensional stability (curl and cockle behavior) and good uptake of the ink fluid can be obtained.
The support according to this invention may also contain additional function layers, e.g., adhesive layers, antistatic layers or non-curl layers, on at least one side.
The support according to this invention is then subjected to a satinizing operation in a known manner. Any desired ink receiving layer for ink-jet printing processes may be applied to the front side of the support. The ink receiving layer may be at least one hydrophilic layer which is suitable for receiving most aqueous inks. An ink receiving layer usually contains a hydrophilic or water-soluble binder, cationic pigment-fixing compounds, pigments and optionally other additives. The coating weight of the ink receiving layer is 5 to 20 g/m2.